The present invention relates to a printed wiring board, and more particularly to a printed wiring board comprising a main printed wiring board of a single-layer or of multi layers, having a wiring pattern of a circuit for performing a desired function and a flexible auxiliary printed wiring board having a wiring pattern for effectively modifying the pattern on the main printed wiring board, and to a method for producing a printed circuit board comprising the above-described printed wiring board and electronic component parts mounted thereon.
A wiring pattern of a printed wiring board (hereinafter referred to as a PW board) is designed and formed to serve a specific function, intended use or the like of the PW board. It sometimes occurs that need for reconstruction arises because of mistake in designing or design is modified. To cope with such a situation, jumper wiring is adopted.
An example of conventional jumper wiring is shown in FIGS. 1 and 2. As illustrated, a wiring pattern and lands 5 are formed on the bottom surface of a substrate 1, and leads 3' of various component parts are made to penetrate through through-holes of the respective lands 6 and are soldered by solder 4 to the wiring pattern 5 and the lands 6. Jumper wires 2 are soldered to connect the lands 6 which are required to be connected together to modify the circuit. Such direct connection by jumper wires between the required points, different from the connection by the wiring pattern on the substrate 1 is called jumper wiring.
The above-described jumper wiring has the following problems. That is, the conventional jumper wiring is conducted manually, one by one, for individual PW boards, and for that purpose wires have to be cut to the suitable length and the insulator of the wires has to be removed or peeled. Such work is time consuming and leads to miswiring. Also, jumper wiring requires skill. For these reasons, productivity is lowered.
A solution to this problem is disclosed in Japanese Utility Model Application Publication No. 9592/1969 published on Apr. 18, 1969. The PW board disclosed therein comprises a main PW board having a wiring pattern and through-holes for mounting component parts, and an auxiliary PW board having through-holes in alignment with certain of the through-holes of the main PW board and jumper wiring formed to connect the through-holes, and pins extending through both of the through-holes of the two boards to achieve electrical connection as well as mechanical coupling between the two boards.
Details of such a conventional PW board is shown in FIG. 3(a), FIG. 3(b) and FIG. 3(c), of which FIG. 3(b) shows a cross section along lines IIIb--IIIb in FIG. 3(a), and FIG. 3(c) shows a cross section along lines IIIc--IIIc in FIG. 3(a).
As illustrated, the main PW board is provided with a printed wiring pattern 5 for providing electrical connection between a land 6 having a through-hole for mounting an electronic component part and another land 6 also having a through-hole. An auxiliary PW board 8 is laid on the main PW board 1, and is provided with lands 6' having through-holes in alignment with the through-holes of the lands 6 of the main PW board 1 and a wiring pattern 9 formed to provide connection to serve for the same purpose as the jumper wires 2 of FIGS. 1 and 2.
Pins 17 shown in FIG. 3(c) provide electrical connection and mechanical coupling of the auxiliary PW board 8 to the main PW board 1. After the auxiliary PW board 8 is laid on the main PW board so that the through-holes of the lands 6' of the auxiliary PW board 8 are correctly in alignment with the through-holes of the lands 6 of the main PW board 1, the pins 17 are inserted in the through-holes of both boards 1 and 8 and soldering is conducted to secure the boards to each other.
With this prior art PW board, manual wiring of the jumper wire 2 of FIGS. 1 and 2 is no longer necessary, but an auxiliary PW board 8 with the required wiring pattern is joined to the main PW board by means of pins and solder, with the result that ommission of or error in jumper wiring can be prevented and the work for jumper wiring is much simplified.
But the above-described PW board has the following disadvantages. First, joining the auxiliary PW board to the main PW board by means of pins and solder requires much work and time and hence increases the manufacturing cost.
Secondly, the thickness of the auxiliary PW board, which is about the same as that of the main PW board makes it difficult to conduct a test after the electronic component parts are mounted and soldered. That is the lead pins of the electronic parts which are made to penetrate through the through-holes of the two boards are not exposed on the bottom side, because of the thickness of the auxiliary PW board, so that a test, such as conduction test is difficult.
In addition, when it is desired to alter, e.g., cut, the wiring pattern of the main PW board after the auxiliary PW board is joined, it is necessary to remove the auxiliary PW board, with the work of the removal involving removal of the pins and the solder. Such work is also time consuming.